Regulation of the scavenging and charging of two-stroke fuel injection internal-combustion engines



July 9,r 1946. B. BoLLl 2,403,844

. REGULATION OF THE SCAVENGING AND CHARGING OF TWO STROKE FUEL INJECTIONINTERNAL-COMBUSTION ENGINES y Filed Sept. 13. 1944 2 Sheets-Sheet l vall?! WOM BOLLI July 9,1946."

2,403,844- CHARGING oF rLwo STROKE REGULATIDN OF THE SCAVENGING AND FUELINJECTION' INTERNAL-COMBUSTION ENGINES Filed Sept. 13, 1944 2Sheets-Sheet 2 MEM-load m. m. m, m

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Patented July 9, 1946 vREGULA'rioN- or THE SCAVENGING AND CHARGING or,Two-STROKE FUEL 1N- l Y JECTION GINES INTERNAL CONIBUSTION EN- BernhardBolli, Arbon, Switzerland, assignor to` Aktiengesellschaft AdolphSaurer, Arbon, Switzerland- Application September 13, 1944, Serial No.553,916

' In Germany July 12, 1943 d 1 5 This invention relates. to internalcombustion engines of the two cycle fuel injection type. It moreparticularly relates to the'regulation of the scavenging and chargingoperation of "such engines operating under highly variable conditions.v. 'f

In engines of thiskindewhich are lprovided with directly drivenscavenging and charging blowers and in the exhaust passage, for thepurpose'of Y obtaining maximum charges and -accordingly weight of freshair is retained in cooperation'with' the scavenging and chargingblower'driven by the engine. In this arrangement the scavenging Yandcharging blower is required to constantly operate against maximumcounter pressure and, therefore, always consumes a maximum of power.

In other engines of this type theclosing of the throttling member in theexhaust passage is automatically controlled in dependence upon theengine speed, in such manner, that thev closing i of the throttlingmember is advanced as the engine speed drops with a view to preventingthe 16 claims. (c1. 12a- 65) tion mentioned above has for its purpose tomaincycle time controlled port areas'from increasing the tainthe'greatest possible rweight of charging air in the working cylinderunder any condition of operation. Therefore, with this kind of regulaztiona maximum torque canbe obtained for instance at every speed oraltitude. However the power demand of the blower driven by the engine isalways equal to the maximum efliciency corresponding to the respectivefull\ load operating condition. In consequence thereof,A in machineswhich frequently must operate under partial load only power consumptionof the blower becomes excessively great within the range of partial loadand vat no load so that :the average fuel consumption of the engine issubstantially raised,

In another known Akind of-engines a by-pass is provided in the blower,to reduce the energy consumed in the` delivery of the scavenging andcharging air within the range of partial load, this by-pass connectingthe pressure side with the suction side and being throttled more' orless. With this arrangement it is possible to reduce the scavenging andcharging pressure to some extent within the range of partial load andthus somewhat to reduce the power consumption, due to the lower deliverypressure. However this delivery pressure of the blower which is equal tothe overpressure of the scavenging air, should be' reduced only to suchan extent that a thorough scavenging ofthe working cylinder is stillwarranted. But since the throttling member arranged in the exhaustpassage is always automatically closed as early as possible the cycletime controlled port area ofthe enginel is always automatically held asize as small as possible. Therefore, with'by-pass regulation of theblower a relativelyV great scavenging pressure corresponding to thissmall cycle time controlled port area throttling member is retardedbeingadvanced as this pressure drops. n

In further known engines the time ofY closing of the throttling memberin the exhaust passage is automatically controlledr in dependence uponthe atmospheric air pressure, that is, the altitude at which the enginevoperates, in such manner, that as the pressure of the atmospheric airdrops athigher altitude the closing `of. the throttling must Yyet bemaintained otherwise appropriate scavenging of the working cylinder isquestionable. The saving in' power consumption of the blower isthusrelatively small, and the blower is highly heated, its eiiiciency isimpaired, and the .volume ofk air passing through the blower is notthoroughly utilized for the scavenging and cooling of the workingcylinder. e

According to'the present invention/these operating Aconditions arefundamentally improved in that the timeof closing ofthe throttlingmember in the'exhaust passage is controlled in dependence upon two'factors of operation jointly,= the control impulse obtained independence upon one operating factor tending to raise the scavenging andcharging pressure as much as possible while the control impulse obtainedin dependence upon the other operating factor tends to reduce as much aspossible the scavenging and charging air pressure within the range ofpartial load and rio-load running. y

While the operating factor that maintains the scavenging and chargingpressure at the highest possible value by varying the time of closing ofthe throttling member may be the engine speed, the scavenging andcharging pressure itself or the pressure of the atmospheric air, thesecond operating factor tending to keep the scavenging and chargingpressure as low as possible is a value which determines the degree ofloading of the engine based, most advantageously, on the quan'- tity offuel to be injected into the engine;

By virtue of this measure according to the present invention, the cycletime controlled port area of the engine is increased when changing overto smaller load. In consequence of this' the volume of air required forscavenging can be conveyed through the engine at a lower pressure. Thescavenging blower then operates at a substantially 'smaller ratio of airpressure so that the energy consumption of the blower becomesaccordingly smaller. Owing to this measure the fuel consumption of theengine decreases to a considerable extent within the lrange of partialload and nio-load running. Fuel consumption is' substantially smallerthan in machines in which cycle time controlled port area cannot bevaried or in the engines in which the thro'ttling member in the exhaustpassage is adjustable only in de-Y pendence upon a single factor ofoperation tending to raise the scavenging and charging pressure to avalue as great as possible regardless of the degree of loading of theengine.

Several embodiments of a device according to' this invention areillustrated diagrammatically in the accompanying drawings in which Fig.1 is a schematic cross section of a two; cycle solid injection internalcombustion engine regulated by controlling the time of closing of thethrottling member in the exhaust passage inv dependence en the enginespeed quantity' of fuel to be injected into the engine;

Fig. 2 shows the corresponding control diagram and Fig. 3 is a diagramshowing the required scavenging pressure in dependence upon the enginespeed with the time of closing of the tlirottling member varying;

Fig. 4 is a diagram illustrating the energy con= sumption of the airblower forming part of the engine shown in Fig. l in dependence upon thescavenging pressure and the engine speed;

Fig. 5 is a schematic cross sectional view of another embodiment inwhich the time of closing of the throttling member is controlled independen'c'e upon the quantity of fuel injected and the scavenging andchargingpressure;

Fig. 6 is a similar View of a third embodiment in which the time ofclosing of the throttling member is controlled in dependence upon thequantity of the fuel injected and the pressure of the atmospheric air,that is, upon the altitude at which the engine operates.

In the embodiment shown in 1 I is the working cylinder which is providedwith intake ports 2 for the scavenging air and exhaust ports 3 for theexhaust gases. In the working cylinder I the working piston 4 isreciprocable' being connected with a crankshaft 5 by a connecting rod I5the intake ports 2 and the exhaust ports 3 being controlled by thepiston 4. In order to provide for retaining a greater volume of chargingair in the cylinder a throttling member 8 actuated by the engine isarranged in an exhaust passage 1 communicating with the exhaust ports 3;

This throttling member here has the form of a butterfly-valve, but itmay also be a rotary slide valve or some other throttling member. It isdriven by the crankshaft 6 of the engine through a pair of spur gears 9,I il, a pair of screw gears H, I 2, a spindle I3, an adjusting sleeveI4, a stub spindle i5 and a pair of bevel wheels I6, I1. The ratio ofgearing of this driving" arrangement may be 110.5; 1:1 or 1:2 withregard to the speed of revolution of the engine, dependent upon theengine construction concerned. The time of closing of the throttlingmember is so chosen that the exhaust passage is shut off before thepiston 4 in its outward stroke again sweeps the intake ports 2. The airhaving entered the cylinder through the intake ports under thescavenging and charging air pressure pL can thus be retained in thecylinder. It is supplied by a blower I8 driven by the engine.

If the engine is intended to operate Within a wide range of speed athighest efliciency, provision must be made that throughout this range,under full load at least, the pressure pli produced by the blower andthus the air Weight available in the cylinder for the combustion can bemaintained at a substantially constant value throughout the entire rangeof speed, This is however; as is Well known, possible only when theentire cycle time controlled intake and exhaust port area of the engineis varied so that as the engine speed drops this area is reduced. i

This isv effected in the kind of engine to which the invention relatesby advancing the closing of the throttling member 8 in the exhaustpassage as'the engine runs at l'ow speed. For this purpose the spindleI3 is provided with straight splines and the stub spindle I5 withsteeply ascending threads. The vtwo spindles are interconnected by theadjusting sleeve I4. If the adjusting sleeve I4 is upwardly displacedthe closing of the throttling member 8 is retarded, whereas in movingthe sleeve downwardly the closing of the throttling member 6 isadvanced.

On the spindle I3 is mounted; a centrifugal governor 2| comprising aspring 22 and a control sleeve 23 Which in operation is adjusted independence upon the engine speed so that as the speed is increased thesleeve rises and is lowered as the speed decreases. The sleeve 23 isengaged by an adjusting lever 24 pivoted at 25 which transmits themovement of the sleeve 23 through a connecting rod Zi to a rocking lever2'I which pivots about a iixed point 28, while its other end engagesAthesleeve I4 to adlust them in accordance with the movement of the governorsleeve 23.

By this means the time of closing of the throttling member in theexhaust passage is adjusted in dependence upon the engine speed so thatas the engine speed risesrthe closing of the exhaust passage by thethrottling member is retarded and is advanced as the engine speed drops.Consequently the cycle time controlled port area of the engine is variedin dependence upon the engine speed;l in 'suchv manner, that lsaid areais reduced as the speed drops and is increased as the engine speedrises.

Fig. 2 showshow the piston opensrthe exhaust ports at point Ao and thescavenging ports at point Saco; at point .S'ps the scavenging ports andat point As the exhaust port slots are closed by the piston. In theabsence of a throttling member in the exhaustv passage compression wouldbegin only at the latter point, and the air weight enclosed in thecylinder when the piston ris in this position would determine themaximum` eiiiciency that actually could be obtained. However, :byarranging a throttling member in the exhaust passage the closingof theexhaust port openings is advanced as indicated for full load by thehatched angularv range qm between points KsI and KSII. At lowest speedsthe closing occurs at KsI incidentalto which the cycle time controlledport 'area is relatively small. At the highest speed the closing occursat KSII at which time saidv port area is materially greater. f.

In Fig. 3 the' scavenging air pressure resulting in a constant volume)op of scavenging 'surplus air is plotted against the engine speed.y Forvarious closing points of the throttling member within a. range betweento 60- away from the lower dead centre the requisite scavengingpressures are plotted in the direction of the axis of ordinates. Thisfigure also shows that in varying this,V closing point of for' example40 *awayl from'thelower dead centre to 0, the said scav enging pressureremains substantially' constant between the greatest and the smallestengine speed as indicated in this figure,V so that the charging airweight enclosed in the cylinder can be maintained at a value greatenough to produce a constant or even an increasing torque 'as the enginespeed drops. The variation ofthe closing time of the throttling memberarranged inthe exhaust passage in dependence upon the engine speedwithin the range KsII in Fig. 2, therefore, has the effect ofmaintaining a scavenging and charging pressure as great as practicallypossible supplyof scavenging air to the working cylinder as required foran appropriate scavenging of the same can then be obtained by means of asubstantially smaller scavenging overpressure pL.

In Fig. 3 the scavenging overpressure required in applying this measureis represented by the chain-dotted curve pL--no load.

According to the present invention this method of regulation istcarriedinto effect in an engine as shown in Fig. l by varying the time ofclosing by the throttling member not only in dependence rear to which arod 32 is pivoted. This rod is throughout the entire range of. engineVspeeds'andV thus also of obtaining a driving torque as great aspractically possible atV each engine speed.

The mode of regulation described above results in substantial advantageswithin the range oi? maximumyload. As s'hown in Fig. 4,y in which thepower consunnotion of the engine driven blower is plotted against theengine speed for different values of the 'scavenging and chargingpressures the blower always presents theV maximum. demand ondrivingpower, thatis, that which is indicated in a dotted curve in Fig.ll at NeG-full load in accordance with the course of the curve 20L-fullload as indicated in Fig. 3. En the part-load operating region as well'as in the no-load condition this relatively great driving power for theblower is highly unsatisfactory from the point of view of vfuelconsumption.

According to the present invention the power consumption is improved inthe operation under part-load and at rio-load in that the driving powerfor the blower is reducedby/decreasing the delivery pressure asindicated by the arrows'in Figv 4. In order to provide for a reductionyof the scavenging pressure it is; however, necessary to extent. This iseffected in suchma-nner that for no-load running the throttling memberis closed only while the air intake of the engine is being closed oronly after it has been closed. :An ample connected in turn with afulcrum 25 on an adjusting lever 24. In varying the fuel quantity byactuating the lever 30 the fulcrum 25 is shifted at the same timein'such manner that this fulcrum i-sflowered as the fuel quantity isdecreased.

Provided that the engine speed remains constant the control sleeve23constitutes the fulcrum for the adjusting lever 24. Therefore, as thefuel quantityv is decreased the adjusting sleeve I4 is raised by thelever 24 through a rod 26 and the rocking lever21 which rocks about afixed point 28 inr consequence whereof the closing of the exhaustpassage Yby the throttling member in the Y exhaust passage is retarded.`During no-load running, i. e. at the lower speed the closing takes placeat point KsIII. At highest speed the closing occurs at point KsIV, whichresults in a range of closing control qm. Therefore, in running atnoeloacl, as indicated in the control diagram lshown inFig. 2, with theengine performing a minimum of revolutions the throttling mernn bercloses at about the same moment at which the piston closes thev intakeports, While, with the engine running at highest'speed of' revolutionthe closing occurs considerably later so that the Working cylinder isclosed only after the piston has movedipast the exhaust ports.

' The principle on which the present invention is based. can be appliedalso to engines in which the variation ofthe time of closing the exhaustpassaage. instead of being dependent on the speed of revolution, iseffected dependent on the scavenging and charging pressure, in suchmanner, that as the scavenging and charging pressure decreases the cycletime'controlled port area is reduced, due to advancing of the closing ofthe exhaust-passage, but is enlarged as the scavenging and chargingpressure rises` due to retardation of the closing, and wherein,therefore, the variation of the time of closing of the throttling memberin dependence upon the said first operating factor "also tends to raisethe scavenging and charging pressure as much as practically possible.

lThe method of regulation off such an engine is schematicallyillustrated in Fig. 5. The governor of the engine used inthe arrangementof Fig. l is here replaced by a pressure cylinder 33 in which'a piston34 is slidably guided. The lower end face of this piston is acted uponby the scavenging and charging pressure pL, whereas the opposite pistonend face is loaded by a spring 35. `Therefore to each scavengingpressure pl, corresponds a certain position of the piston 34. Under ascavenging pressure as required for running at minimum speed ofoperation and under 7 full load the piston 34 abut's iigailisty a stop36. The piston 35 is connected by means of a rod 37 with the adjustinglever 25 which pivots on an adjustable ful'crum 25 as in the firstembodiment. With the scavenging pressure @L dropping the piston 34descends. The adjusting sleeve i4 is lowered by means of the lever 24,the rod 26 and the rocking lever 2l, in consequence whereof, the closingof the throttling member is advanced and the cycle time controlled portarea is reduced so that the scavenging and charging pressure is raisedto a higher value again. The scavenging and charging pressure is thusmaintained at a value as high as practically possible in accordance withthe characteristic of the spring 35.

According tc the present invention the ulcrum of the rocking lever 24 isconnected by means of the rod 32 with the admission lever Sli of thefuel pump, In changing over to part-load operation the fulcrum 25descends, whereby the clos-ing movement of the throttling member` isretarded. The scavenging pressure will drop while the piston 3.4i movesdownwards, vtherebyV first to oppose the control movement. However, asthe piston 34 then bears against the stop 36, in further decreasing thefuel injection quantity, the adjusting sleeve hl will be readjusted sothat the closing of the throttling member is further retardcd.

During running at no-load the throttling member shuts off the exhaustpassage at each revelution as late as at the points KSIII and KsIV,which in this case coincide, that is, only after piston 4 has coveredthe intake ports 2. Therefore, with the engine running under part-loador at nc-load the scavenging and charging pressure is also reduced to aminimum still sufficient for an appropriate scavenging, whereby, thedriving power required for the blower is materially reduced. Y

In engines operating with solid injection which are required to operateat widely varying altitudes, the controlling of the closing time by' thethrcttling member in the exhaust passage can also be effected inuependence'upcn the' altieV tude i. e. the atmospheric air pressure. Inso varying the cycle time controlled port area of the' engine thedropping of the scavenging and' charging pressure at rising altitudecounter# acted, whereby here also the 'regulation has the effect toraise the scavenging and charging' air pressure to a practicallypossible maximuml In order to reduce the power consumption of the blowerwhen running under part-load or at no=load and to reduce the fuelconsumption the regulation of the closing time can in principle again beeffected in dependence upon a second factor of operation which consistsin the fuel in: jection quantity, so as to reduce, when under pa-rtsloador at rio-load, the scavenging' and charging pressure to a minimum whileranting a satisfactory scavenging.

In Fig. 6 the regulating device for an engine of this kind isschematically illustrated-f. The governor for regulating the speed ofrevolution as shown in Fig. l and the pressure cylinder shown in Fig. 5respectively 'are here replaced by a flexible barometric cell 3B. Theend '39 vcf this capsule is attached to a lxfed point whilst the freeend de of the cell is arranged on the adjusting lever 24 as described inconnection with the preceding examples, 'Io` every altitude I-Icorresponds a predetermined length of cell and thus a certain positionof the pivot joint 40. As the altitude of operation increases the cell 8elongates and the pivot joint 40 moves downward so that by means of theadjusting lever 24, the

rod 26 and the rocking lever 21 the adjustingv sleeve I4 is displaceddownwardly which results in advancing the time of closing of thethrottling member. The spindle l3is formed with splines I9, the stubspindle l'with steeply ascending threads. The two spindles are connectedby the adjusting sleeve I4, the top end of which is threaded inwardly Ifthe sleeve I4 is lifted, it will retard the closing movement of thethrottling member 8, whereas, if the sleeve is moved downwardly, theclosing movement is advanced. I-Iereby the cycle time controlled portarea of the engine is reduced and the supply of scavenging air which, ifthis area were left unchanged, would increase as the altitude ofoperation increases, is maintained constant so that the blower isrendered capable of maintaining a substantially unchanged chargingWeight in the Working cylinder even if the altitude of operationincreases.

At lowest altitude of operation Ho` (an aircraft resting on the ground)the closing point is represented by KsII. At greatest altitude HumV theclosing point is represented by KsI. In changing over from part-load tono-load running also in this engine the scavenging and charging pressurecan be lowered to a minimum allowable value still sufficient forappropriate scavenging, by enlarging in accordance with theinvention'the cycle time controlledl poit area, for the purpose ofeconomizing in blower output and driving power. In this kind ofregulating device also the arm extension 3l of the admission controllever 30 is connected with the fulcrum 25 of the rocking lever 24 bymeans of a rod 32.

In order to decreasev the fuel quantity to be injected the fulcru'm 25can be lowered. At a certain altitude I-I the fulcrum is constituted bythe pivot joint 68. Through the rod 26 and the rocking lever 21 theadjusting sleeve is displaced upwardly so that the point of closing ofthe throttling member is advanced, By this means the cycle timecontrolled port area of the regulating device is enlarged and thescavenging and charging pressure is reduced. The driving powerconsumption required by the blower is thus substantially decreased inrunning under part-load and at no-load and the demand on fuelconsumption p by the engine in synchronism therewith and coinmunicatingwith the intake ports, an exhaust conduit communicating with the exhaustports, an engine-driven throttle in said exhaust conduit and mechanismfor controlling the closing moveil ment of said throttle in dependenceupon the quantity of fuel injected 'and the engine speed jointly in suchmanner that the closing movement 'of said throttle is retarded, as thequantity of injected fuel drops, and is advanced as the v engine speeddrops'.

2. The engine Of claini 1', in which the throttle f 9 control mechanismis arranged to operate in dependence upon the quantity of fuel injectedand the scavenging and charging air pressure, the closing movement ofthe throttle being retarded as the quantity of injected fuel drops, andbeing advanced, as the scavenging and charging air pressure drops.

3. The engine of claim 1, in which the throttle control mechanism isarranged to operate in dependence upon the quantity of fuel injected andthe atmospheric air pressure, the closing movement of the throttle beingretarded as the quantity of injected fuel drops, and being advanced, asthe atmospheric air pressure drops.

j 4. The method of operating two-stroke cycle internal combustionengines provided with means for forcing in air for charging andscavenging in synchronism with the engine revolutions, which comprisestiming the discharge of exhaust gases in synchronism with the operatingcycle, supplying fuel for combustion and throttling the discharge ofexhaust gases in dependence upon the quantity of fuel injected and theengine speed in such manner that throttling is retarded as the quantityof injected fuel drops, and is advanced as the engine speed drops.

5. The method of claim `4, in which the discharge of exhaust gases isythrcttled in dependence upon the quantity of fuel injected and thescavenging and charging air pressure jointly, the

